def karatsuba(a, b):
    """ Multiplies two integers a and b using karatsuba's algorithm
    """
    if len(str(a)) == 1 or len(str(b)) == 1:
        return (a * b)
    else:
        m1 = max(len(str(a)), len(str(b)))
        m2 = m1 // 2

        a1, a2 = divmod(a, 10**m2)
        b1, b2 = divmod(b, 10**m2)

        x = karatsuba(a2, b2)
        y = karatsuba((a1 + a2), (b1 + b2))
        z = karatsuba(a1, b1)

        return ((z * 10**(2*m2)) + ((y - z - x) * 10**(m2)) + (x))
